In flourite structure `(CaF_2)`-

Options

A. `Ca^(2+)` ions form ccp & `F^(-)` ions are present in all the tetrahedral voids
B. `Ca^(2+)` ions form ccp & `F^(-)` ions are present in all the octahedral voids
C. `Ca^(2+)` ions form ccp & `F^(-)` ions are present in half of the octahedral voids and the rest half ions in the tetrahedral voids
D. None

Answer

To solve the question regarding the fluoride structure of \( \text{CaF}_2 \), we need to analyze the positions of calcium ions (\( \text{Ca}^{2+} \)) and fluorine ions (\( \text{F}^- \)) within the crystal lattice. Here’s a step-by-step breakdown:

### Step 1: Understand the Composition of \( \text{CaF}_2 \)
- \( \text{CaF}_2 \) consists of calcium ions with a charge of \( +2 \) and fluorine ions with a charge of \( -1 \).
- The formula indicates that for every \( \text{Ca}^{2+} \) ion, there are two \( \text{F}^- \) ions.

**Hint:** Remember the charge balance in ionic compounds; the total positive charge must equal the total negative charge.

### Step 2: Identify the Structure Type
- \( \text{CaF}_2 \) adopts a fluorite structure.
- In this structure, the calcium ions occupy specific lattice points, while the fluorine ions occupy the voids created by the arrangement of calcium ions.

**Hint:** Familiarize yourself with common crystal structures and their characteristics, such as coordination numbers and types of voids.

### Step 3: Analyze the Coordination of Ions
- In a cubic close-packed (CCP) arrangement, there are two types of voids: tetrahedral and octahedral.
- The number of tetrahedral voids is double that of octahedral voids in a CCP structure.

**Hint:** Recall that in a CCP structure, the tetrahedral voids can accommodate more ions than the octahedral voids.

### Step 4: Determine the Positions of Ions
- Since there are twice as many fluorine ions as calcium ions, the \( \text{F}^- \) ions will occupy the tetrahedral voids.
- The \( \text{Ca}^{2+} \) ions will occupy the lattice points of the CCP structure.

**Hint:** Visualize the arrangement of ions in the crystal lattice to better understand where each type of ion is located.

### Step 5: Conclusion
- The correct arrangement is that \( \text{Ca}^{2+} \) ions form the CCP structure, and \( \text{F}^- \) ions occupy all the tetrahedral voids.
- Therefore, the correct answer is that \( \text{Ca}^{2+} \) forms CCP and \( \text{F}^- \) occupies all tetrahedral voids.

**Final Answer:** \( \text{Ca}^{2+} \) ions form CCP, and \( \text{F}^- \) ions occupy all tetrahedral voids.

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